1. Field of the Invention
The present invention relates to a lockup clutch for a torque converter with an axially displaceable piston for transmitting a torque from a drive side to a driven side of the torque converter. The piston is connected to a turbine wheel of the torque converter via a torsional vibration damper. The torsional vibration damper has an input part which is connected with the piston so as to be fixed with respect to rotation relative to it and an output part which is connected with the turbine wheel so as to be fixed with respect to rotation relative to it. A plurality of torsional damper springs are arranged between the input part and the output part distributed along the circumference of the torque converter such that a relative rotation is possible between the input part and the output part along a determined angular area. The torsional vibration damper has an individual cover plate connected directly with the turbine wheel having an axial securing device for the torsional damper springs.
2. Description of the Related Art
A prior art torque converter having a lockup clutch with a torsional vibration damper arranged between the piston of the lock up clutch and the turbine wheel of the torque converter is known, for example, from DE 197 21 642 C1. This torque converter is constructed so as to be quite narrow in the axial direction because only one cover plate is provided for the lockup clutch. The torsional vibration damper has an input part which is connected with the piston so as to be fixed with respect to rotation relative to it and an output part which is connected with the turbine wheel so as to be fixed with respect to rotation relative to it. A plurality of torsional damper springs are arranged between the input part and the output part distributed along the circumference of the torque converter such that a relative rotation is possible between the input part and the output part along a determined angular area. The input part of the torsional vibration damper contacts one end of a damper spring of the torsional vibration damper by its control edge and the output part contacts the other end of the damper spring by its control edge. During a relative rotation of the input part and output part the torsional damper springs are compressed, thereby damping torsional vibrations. Holding cams are provided for the axial securing of the torsional damper springs. However, the springs can bulge out in the axial direction when acted upon by force and contact the piston. The contact leads to wear of the piston during torsional vibrations.